Building Pathology and Forensic Engineering

Table of Contents

Question 1: Five key points to consider when using copper as an external building material

Question 2: Two protection methodologies commonly used in aluminium and considerations

References

Firstly, copper is a really durable cladding material thanks to some benefits as below. Copper is one of the best materials for roofing because of its excellent water resistance. Copper as sheet metal supports a nearly continuous resistant water that covers minimum number of joints between sheets. Moreover, these coper sheets can cover roof slopes at lower pitches than using roof coverings. As the result, these coper sheets allow a smoother surface for curved lines of roof. In additional, high tensile strength and low thermal movement of copper sheet minimize the creep or stretch caused by thermal change to make it easier to be installed at high steep pitched roof than other materials. Moreover, thanks to its physical characteristics as high melting point, it makes coper sheet has high fire resistance. Therefore, these sheets are used in important and expensive buildings. Under raining conditions or salty environment, the surface of copper sheet is oxidized, but it creates the unique green tarnish or patina coating to protect the metal beneath. This reduces the corrosion speed of copper sheet to make it stand for more than 100 years. Besides that, to reduce the stain on copper sheets surface due to heavy rain, using gutters to drive water far away from roof by downspouts and having at least 1 inch of drip edge (Building Conservation 2012).

Another characteristic that makes copper sheeting become one of the best roofing materials is its lightning protection. Thanks to its perfect electrical conductivity, copper sheet transmits lightning energy quickly to the earth via gutters and downspouts to prevent building from damage caused by lightning strike (Copper Concept 2006).

However, due to its very high galvanic number or called nobility, the other metal material structures that contact to copper sheets are easy to be corrosion. Therefore, there is a need of using separating materials between them like some kinds of paint, metals with gasket. To substrate for copper sheets, the best material should be timber especially Fire Retardant Treated (FRT) plywood. Other choices could be concrete, masonry, brick or terra cotta. To make water resistance and to harden the joints and seams between coper sheets, continuous long run of soldered seams and joints would be the best choice for copper sheets (Copper Development Association 2019).

Secondly, copper cladding is a Cost-effective material thanks to its durability, easy to maintenance so the maintenance cost for roofing is really low. Nowadays, technology like prefabrication or mechanised seaming help to reduce cost in mass production for copper cladding. Moreover, copper is one of the metals has low density but very high tensile strength. This combination helps to reduce size and weight of copper sheet to make it become light weight material. So, there is a smaller number of structures to support it to reduce a huge cost for structures that support underneath these sheets for roofing. Copper roofing is even less expensive than lead, slate or artificial clay tiles (Copper Concept 2006).

Thirdly, copper cladding is an Antimicrobial material. According to the research in USA, thanks to its antimicrobial characteristic, copper cladding is used in hospital rooms to drop the amount of Healthcare Acquired infections (HAIs) around 58% versus rooms that are cladded with other materials. That research also stated that copper cladding can kill 83% bacteria that create HAIs within only 2 hours. These viruses also can not regrow within these rooms cladded by copper. Especially in Australia, HAIs virus is the cause of about 9,000 deaths of patients. Therefore, copper cladding is the best material for hospital and aged care not only in Australia but also worldwide (Architecture and Design 2013). 

Fourthly, copper cladding is a Sustainable refurbishment material thanks to its Embodied Energy which is the sum of all energy during phases of life cycle from mining to final production needed to make copper sheet is 103.3 MJ/m2 that is lower than stainless steel (157.2) and aluminium (115.4) (Copper Concept 2006). In additional, the amount of CO2 emissions to produce copper is 6.6 kg/m2 which is lower than stainless steel (10.9) and aluminium (7.5) that help to reduce global warming (Copper Concept 2006). These factors make copper becomes a sustainable refurbishment material. Moreover, thanks to its durability, cladding materials made from copper need minor repair or replacement to reduce energy needed for these processes. Besides that, it is highly recyclable because it can be recycled without loss in strength. It is a highly reusable material, has minimum effect on natural resources (Copper Alliance 2019).

Finally, copper sheets have a unique colour and shine. All over the world, there is no metal, exception for gold, has colour like copper. When it is exposed to the environment, copper’s shiny red convert to brown and then become to its unique green tarnish or patina that is result from oxidization of copper (Copper Development Association 2019).

The first method used to protect aluminium is Liquid Coating. When installing aluminium window frames to masonry walls, without protection, aluminium frame contact with cement materials can damage the frame because aluminium reacts with alkali hydroxides from fresh cement to create corrosion for aluminium. As the result, there must be liquid coating material for aluminium frame such as organic paint or anodized aluminium. High quality coatings are fluorocarbon, siliconized polyesters or acrylics. The minimum thickness of coating should be 20 microns. Moreover, the inorganic coating like anodized finishes on aluminium frame can turn surface of aluminium to aluminium oxide which is a very durable surface. After that, painting a clear organic liquid coating to protect the anodized aluminium surface. In additional, when installing aluminium frame to masonry walls, wet mortar and concrete must be removed quickly from aluminium frame (PCA America’s Cement Manufacturers 2018). Liquid coating on aluminium is very good for coating thin film and inexpensive (Thomas 2019).

Another method used to protect aluminium frame window and internal finishes is Powder Coating. This method provides a more durable thicker coating layer for aluminium. It also effects to environment less than liquid coating method. The powder coating layer is a hard finish that have both protection and decoration functions. It can resist to hard impact, extreme weather, moisture much more than liquid coating even with the same thickness of coating. The aluminium window frame with powder coating can also insulate electricity and have a brilliant colour after contacting to heavy rain or strong sunshine. Thanks to powder is solid coating material, this method can save quantity of coating material required and energy for curing and drying process. Considering environment aspect, powder coating on aluminium frame does not need solvents like liquid coating that have VOCs which is very harmful to environment. Moreover, this method produces less CO2 and zero hazardous waste. Especially for aluminium, the normal primer applied to it has chrome which is already very toxic. Therefore, powder coating for aluminium can reduce a lot of harmful by-products to environment. However, this method can not give a thin coating layer on aluminium surface and it is quite expensive for the first investment on coating equipment than liquid coating (Thomas 2019).

In conclusion, Liquid coating method to protect aluminium frames and internal finishes for residential houses is more suitable than Powder coating method which is suitable to commercial building. 

Architecture and Design 2013, Study reveals healthcare benefits of copper surfaces. [Online] Viewed 2 February 2019, https://www.architectureanddesign.com.au/news/study-reveals-healthcare-benefits-of-copper-surfac#

Building Conservation 2012, Copper Sheet Roofing. [Online] Viewed 2 February 2019, http://www.buildingconservation.com/articles/copper-sheet-roofing/copper-sheet-roofing.htm

Copper Alliance 2019, Renewable Energy. [Online] Viewed 2 February 2019, https://copperalliance.org/benefits-of-copper/sustainable-energy-renewable-energy/

Copper Development Association 2019, Inspiring Architects with Copper’s Sustainable Contributions to the Building Construction Market. [Online] Viewed 2 February 2019, https://copperalliance.org.uk/about-copper/applications/architecture/?fbclid=IwAR1n4wlLEdr5BkcbXWWQFvLAL7q8mtstKiVY5ueU7lNGnCYtaKpGvgSU88I

Copper Development Association 2019, 1.3. Architectural Considerations. [Online] Viewed 2 February 2019, https://www.copper.org/applications/architecture/arch_dhb/technical-discussion/fundamentals/arch_considerations.html

Copper Concept 2006, The Guide to Copper in Architecture. [Online] Viewed 2 February 2019, https://copperconcept.org/sites/default/files/attachment/2011/pubpdf145.pdf

PCA America’s Cement Manufacturers 2018, Aluminium Frames in Masonry Walls. [Online] Viewed 3 February 2019, https://www.cement.org/learn/materials-applications/masonry/masonry-construction/aluminum-frames-in-masonry-walls?fbclid=IwAR0pNN3K9t37PqRIiXfbV7BxoZIf6x1s4aAjM231tIHPVVuzo9ApIoXsSjk

Superdraft 2019, 4 Benefits of Building with Copper. [Online] Viewed 2 February 2019, https://www.superdraft.com.au/blogs/4-benefits-building-with-copper?fbclid=IwAR3bqU4E0kwbdawBrKfXkQDmjZxFc3KlUycCtf-birbdo6thzbs1wf7QP20

Thomas 2019, Benefits and Limitations of Powder Coating. [Online] Viewed 3 February 2019, https://www.thomasnet.com/articles/custom-manufacturing-fabricating/powder-coating-pro-con/